| Cushioning materials is widely used in product packaging to decrease the damage caused by vibration and pound during transportation and storage.But most of cushioning packaging materials at this stage still exist some problems,such as consumed non-renewable resources,non-degraded and poor cushioning properties.It's very essential to develop the new cushioning packaging materials with more eco-friendly and lightweight.Luffa is a kind of natural material with excellent energy absorption characteristic,which is derived from its unique hierarchical cellular structure.Inspired by this natural structure,this paper chose natural luffa sponge material for bionic object,analyzed its structure characteristics and the relationship between the structure and properties.A biomimetic model was designed by extracting the typical luffa sponge structure model.Then greater available natural palm fiber was chosen to prepare cellular material with luffa sponge structure characteristic.And the manufacture process and technological parameters were studied and analyzed.The main work of this paper is as follows:In this paper,the structure and mechanical properties of natural luffasponge were studied firstly.The results of axial static compression test showed that:(1)The stress-strain curve of luffa sponge covered the elasticity region,the yield stage and the densification region and the stress-strain curves show a near constant plateau stress over a long strain range.Which is an ideal absorbing material.(2)With the increase in density,the yield strength,plateau stress and energy absorption capacity per unit volume of the luffa sponge were increased,while the densification strain was reduced.(3)The mechanical properties of luffa sponge is closely related to its hierarchical cellular structure.The inner surface enhanced the total stress level and energy absorption capacity.The soft cellular hoop wall and core part provide constraints for buckling of inner surface and changed its damage pattern.Due to various combination of factors makes luffa sponge have the characteristics of lightweight,stable and energy absorption.Then the structure and energy-absorbing principle of luffa sponge were analyzed in theory.A biomimetic model was designed according to the structure and properties of the luffa sponge.Next palm fibers were used as the main ingredient,natural latex as adhesives,the biomimetic cushioning packaging material was prepared by combination of microwave heating and hot pressing method.Through a large number of trials,the technology parameters was determined,that is,microwave power is 600 w,heating time is 4min.Hot-pressing conditions are the hot-pressing temperature is 140?,hot pressing pressure is 0.5 MPa,hot pressing time is 15 min.Finally,the mechanical and cushioning properties of the material were tested and analyzed.Results showed that the palm fiber cushioning material has higher platform stress and better energy absorption performance compared with polyfoam,and has lower elastic modulus and initial peak stress compared with the honeycomb paperboard within the scope of the density(density ranges from 0.06 to 0.1 g/cm~3)prepared in this dissertation.It is close to overcoming the negative influence caused by"stress peak"of honeycomb paperboard.The palm fiber foaming cushioning material has good cushioning and energy absorption properties.On the one hand,this study provides scientific and effective data for thecomprehensive utilization of natural luffa sponge materials and the design of porous materials based on the luffa sponge structure.On the other hand,the palm fiber foaming cushioning material fully utilizes waste palm fibers,that could replace polyfoam as cushioning materials to some extent.The purpose of saving natural resources and reducing environmental pollution is achieved. |
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